I have a 2007 Chevy 3500hd dump with the 6.0L gas and 4.10 gears. That thing only gets 7-8 mpg and it doesn't matter if I'm loaded or not. I have a few friends with F450/F550 Vito the v10 gas and 4.88 gears. They are reporting 6-8 mpg. At those numbers all you can do is hope/pray that gas doesn't go over $5